Semiconductor signal translating device



y 15, 1952 R. J. KIRCHER 2,603,693

SEMICONDUCTOR SIGNAL TRANSLATING DEVICE Filed Oct. 10, 1950 FIG./

SEMICONDUCTOR /6 13 \METAL J- lN l/E N TOR R. .4 K/RCHER ATTORNEY Patented July 15, 1952 ,fUNITED STATE C SEMICONDUCTOR SIGNAL TRANSLATING DEVICE Summit, N. J., assig'nor aboratories, Incorporated,

Iteymond J. Kireher,

to Bell Telephone L Y., a corporation of New York New York, N;

Application October 10, 1950, Serial No.-189,387 I.

8 Claims. (01. 115-366) #This invention relates to semiconductor si nal translating devices and more particularly to semi-conductor amplifiers of the type disclosed in the application Serial No. 33,466, filed June 17, 1948, of-J. Bardeen and W. H. Brattain, now Patent 2,524,035, granted October 3, 1950.

Devices of this type comprise, in general, a body of semic'onductive material for example germanium, a pair of connections, for'example point contacts, designated the emitter andcol- 1ector, to the body, and a third substantially ohmic connection, referred to as the base, to the body. .Electrical carriers of sign opposite that of thosenormally in excess in the body are injected at the emitter and flow to the collector wherebyamplified replicas of input signals impressed between. the emitter and base, appear in a load. circuit connected between thecollector and base. .The semiconductive body may be of either ,conductivity type, that is N or P-type. As .is knowngeach type is associated with impurities characteristic thereof, specifically excess donor impurities'in the case of N-type material and excess acceptor impurities in the case of P-type material. If the body is of N-type, the carriers normally in excess in the bulk thereof are "electronsand the. carriers injected .at the emitter are holes- On the other hand, if the body 'is of P-typ e, the carriers normally in excess" in the bulk-thereof are holes and the injected carriers are electrons. l ---It .has beenfound that in such devices the operating. characteristics may vary from unit to unit and that, further, individual units are subject to instability as evidenced by oscillatory phenomena. i I g Onegeneral object of this invention is to improve the performance of semi-conductor signal translating devices such as amplifiers. More specific objects of this invention areto' enhance the stability of such devices and to increasethe uniformity of product in the manufacture of; the devices. l 1 ,It has been determined that ins'tablity of ideof the .typefhereinabove' referred this at: to 'the' sporadic .gjen eration forinjection of carriersv in or intoijithe body. byv mechanisms jdistinct from the emitter tributabl'e' in many cases andlthat" one source of such unwanted carriers is at the base connection. Specifical1y,,'at the base connection in a device. embodying an'N-conductivity type semiconductor body, holesmay be injected into the body from the base electrode and these 'deleteriously effect the functioning of the device. Similarly, in devices including a P-conductivity type body,.electrons may be injecte d into the ,body from the base with consequent degradation of the performance charac: teristics ofthe device. r

In accordance with one feature of this. inven-. tion, such emission or injection of carriers at the base connection is substantially inhibited. This is effected by establishing between the base electrode and the semiconductive body a barrier to the flow into the semiconductor body from the base electrode of,carriers of the sign like that of those introduced intentionally at the emitter, that is of thesign opposite that of those normally in excess of the body. .Such abarrier is created by producing at the body-electrode interface a region or zone in which the .concentration of impurity characteristic of-the conductivity type of the body is greater than that in thebulkof thebody. 1

In one specific embodiment of this invention wherein the body is of N-conductivity type, a

donor impurity is introduced into the :surface portion of the body to which thebase connection is made, thereby to make, aregion-yofthe body contiguous with the base electrode; more. strongly N.-type than the bulk of the body. The

' donor impurity may be introduced, forexamplc, by utilizing a tin-antimony solder for afiixing the base electrode to the body orfby plating the surface with antimony and. affixing thebase electrode to the plated surface under conditions effecting diffusion of the antimony into. the body. The, invention :and the above-noted and other features thereof --yvill be understood more clearly and fully from the following detailed descrip: tion with reference to the accompanying draw:

am-whi Fig. 1 depicts a semiconductor amplifier illus-. trative of one embodiment of thisinventloni; and I 3'- .Fig. 2 is 1 a sectionalview to an enlarged-scale ia t on Q1. v mp i e se i c o s uc u .11; x 1 z In the;drawing, for the sake of clarity, di;- mensions of; the semiconductive j body have: been greatly exaggerated. In a, typical-device, the

em e n u five. y st n 100. 5.0 aside'and about 12 milsthick. I Referring now to the drawing, the signal translating device illustrated in Fig. 1 comprises a body' 10 .of semiconductive material, for ex-. ample of germaniumor silicon, ofeither con-.- ductivity type. The germanium material may 5 connected to said body, and means comprising an acceptor material in excess of that in the bulk of said body defining a barrier at the junction of said base electrode and said body. 7

5. A signal translating device comprisin a body of N-conductivity type germanium, emitter and collector connections to said body, a base. electrode, and a solder containing a donor imconnection to said region.

7. A signal translating device comprising a body of P-conductivity type germanium having at one surface thereof a region containing acceptor impurity in excess of that in the bulk of Number 6, the body, emitter and collector connections to said body at points spaced from said region, and a base connection to said region.

8. A signal translating device comprising a body of N-conductivity type germanium having at one face thereof a region containing antimony and of greater donor impurity concentration than the bulk of said body, a base connection to said region, and emitter and collector connections to the opposite face of said body.

' REYMOND J. KIRCHER.

REFERENCES CITED The following'references are of record in the file of this patent:

UNITED STATES PATENTS Name Date 2,524,035 Bardeen et al. Oct. 3, 1950 

